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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - DivRemPairs is incorrect in the presence of undef"
href="https://bugs.llvm.org/show_bug.cgi?id=42619">42619</a>
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<th>Summary</th>
<td>DivRemPairs is incorrect in the presence of undef
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Scalar Optimizations
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>nunoplopes@sapo.pt
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, regehr@cs.utah.edu, spatel+llvm@rotateright.com
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<pre>See, for example:
$ opt -div-rem-pairs Transforms/DivRemPairs/X86/div-rem-pairs.ll
define void @decompose_illegal_srem_same_block(i32 %a, i32 %b) {
%rem = srem i32 %a, %b
%div = sdiv i32 %a, %b
call void @foo(i32 %rem, i32 %div)
ret void
}
=>
define void @decompose_illegal_srem_same_block(i32 %a, i32 %b) {
%div = sdiv i32 %a, %b
%1 = mul i32 %div, %b
%2 = sub i32 %a, %1
call void @foo(i32 %2, i32 %div)
ret void
}
Transformation doesn't verify!
ERROR: Source is more defined than target
Example:
i32 %a = undef
i32 %b = #x00000001 (1)
Source:
i32 %rem = #x00000000 (0)
i32 %div = undef
Target:
i32 %div = #x7fffffff (2147483647)
i32 %1 = undef
i32 %2 = undef</pre>
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